In order to bend metal plates, there are known in the art machines which include a horizontal table supported by two vertical posts and provided with a clamping mechanism which can be pressed on the top surface of a metal plate lying on the horizontal table. The shape of the front edge of the horizontal table corresponds to the shape of the bend imparted to the metal plate. In order to perform the bending operation and force the metal plate around the front edge of the horizontal table, there is provided a rotatable apron mounted on two pivoting arms which rotate in coaxial spindles. In these known bending machines, the spindle axis must coincide with the curvature axis of the bend imparted to the metal plate.
It will be appreciated that the relative positions of the table, of the plate clamping mechanism and of the spindles around which the apron rotates must all be properly determined on the basis of the thickness of the plate to be bent and the radius of curvature of the bend imparted to the plate. In some machines, accommodations for various thicknesses can be made by moving only the horizontal table which requires a relatively complex mechanical system and the mobility tends to reduce the overall rigidity of the table and the side posts.
In still other known machines, only the spindles are movable vertically within the housing and this movement also requires a complex mechanism which, however, normally does not diminish the overall rigidity of the table-side posts assembly.
In both cases however, adjustments must be made whenever plates of different thicknesses are to be bent or when the radius of curvatuve to be imparted to the plates is changed.